This invention relates to alloy systems containing hard particles, such as particles of TiC.
Historically, TiC alloys have been formed by “cementing” very hard TiC powder (Vickers 3200) using binders made of nickel, molybdenum, niobium, and tungsten, with the binding elements typically constituting about 40 to 50% of the total weight of such an alloy.
Historically these TiC alloys are formed using powder metallurgy techniques from very fine particles, in particular, materials having a particle size under 20 microns, with a substantial portion being under 6 microns.
The hardness of such TiC alloys makes them attractive for use in ballistic armor and other applications, but the brittleness properties of such alloys is a drawback.
The metals historically used for binding in TiC alloys have relatively high densities, in particular, nickel at 8.9 g/cc, molybdenum at 10.22 g/cc, niobium at 8.57 g/cc, and tungsten at 19.3 g/cc. As a result, such composite TiC alloys have had a density of about 6 g/cc or higher. Materials of that high density are disadvantageous for ballistic armor, for which low weight is an important feature.
A new composite system described herein has superior properties, being not only hard, but also being much lighter in weight than 6 grams/cc and having better toughness characteristics than previously reported TiC alloys.
The composite systems described herein are formed from a hard powder as described herein, such as a TiC powder, combined with a green binder system of titanium sponge granules and/or other titanium powders and a binder system comprising titanium, nickel, and aluminum provided either as a master alloy or as elemental powders, which then are compressed and sintered. It is observed that the nickel forms lower melting point eutectoid-like structures when combined with the titanium of the green binder system.
Bodies of TiC composite systems described herein can bind with bodies of titanium or other materials, allowing for the production of layered composite armor structures. Such layered composite structures can have advantageous attachment configurations, and favorable weight, ductility, and ballistics properties.